The present invention relates generally to a structure such as a retaining wall for providing an abrupt change in the elevation of a ground surface. More particularly, the present invention concerns to a new and improved wall facing and a method of construction whereby the wall face can be essentially covered with live plants.
Many years ago, a new and improved earth stabilization technique was developed and successfully marketed which makes use of precast concrete facing elements to cover the exposed face of a gravity structure created by a composite material. The composite material as fabricated from layers of particulate backfill material which alternate with layers of reinforcing members attached to the facing elements. Frictional interaction between the particulate soil and the reinforcing members stabilizes the composite material structure thereby creating a gravity wall. The foregoing technique is applicable to retaining walls and the foregoing description is generally covered by U.S. Pat. No. 3,421,326, issued Jan. 14, 1969 to Henri Vidal entitled Constructional Works.
The general technique of earth stabilization has also been employed in connection with gravity walls having an inclined face. In this instance, special wall facing elements were designed with a face that is generally parallel to the inclined face and which lies in the plane of the inclined surface. These wall facing elements provide a smooth wall surface and are positioned in the wall with a pair of generally triangular gussets that support the wall in its inclined position. Sloped walls using the general earth stabilization technique and wall facing elements for use in connection therewith are described in U.S. Pat. No. 4,125,970, entitled "Bulk Storage Facility," issued to Henri Vidal on Nov. 21, 1978.
Various other types of facings have also been contemplated for use in connection with stabilized earth structures of the type described. For example, it has been proposed to use commercially available precast bridge sections for a facing material by setting those sections on end and connecting them to the reinforcing elements. Such a facing has a pair of generally continuous vertical webs which project forwardly from the face of the wall. Such a facing structure has been described, for example, in the reports of an International Conference on Soil Reinforcement, see held Mar. 22, 1979 in Paris, France, Vol. II, pages. 447-48.
There have also been uses of the frictionally stabilized earth masses in terraced arrangements for use in walls. Examples of such terraced arrangements are the retaining walls constructed at Vail Pass, Colorado. In those retaining wall structures, the wall facing elements are generally concave with vertically extending cylindrical surfaces. Successive terraces were benched from one another with the result that a generally continuous concrete face is presented by the various retaining wall portions.
The various techniques of providing facings for frictionally stabilized earth structures have in the past been characterized by an essentially continuous concrete face which is either vertical or inclined at some angle relative to the vertical. Such face structures are not well suited for use in scenic environments where the presence of large exposed concrete faces is aesthetically unsuitable. Moreover, the hard generally planar face is not well suited for absorbing sound which would be reflected from the surface. And, such wall structures are very obvious when used as visual barriers or a security barriers.
To date, no frictionally stabilized earth structure has been available which provides a face that is capable of supporting growing plants to at least partially mask the underlying structure. In particular, there have been no precast concrete elements which have been suitable for such a wall.
To date, there has been no method of building a frictionally stabilized earth structure with a face that can be essentially masked by plants.
It is, therefore, an object of the present invention to provide a novel wall facing element which is adaptable for construction of a wall with a face essentially covered by plants.
Another object of the invention is to provide a wall which can have a vertical face that is masked by plants.
It is a further object of the present invention to provide a wall facing which can have sound absorbing properties and which is uniquely adapted for situations where concrete faced retaining walls are unsuitable.
These hitherto desirable but unavailable features are now provided by a wall erected with facing elements that provide an inclined surface which extends into the wall face itself and provides generally horizontal ledges running longitudinally along the wall. These ledges are well suited for various plantings that can partially or entirely mask the wall face, that may grow to a height approximately coextensive with the wall facing panels themselves or that may hang downwardly over the facing panel below. For vertical support, each facing panel is provided with a buttress that projects forwardly from the panel but not beyond the vertical plane passing through the upper edge of each panel. In this fashion, the wall can have successive horizontal rows of wall facing panels which present a vertical face or an inclined face, as desired.
In order to reduce the bearing pressure of the wall facing elements on the underlying soil material, the buttress may be provided with a downwardly increasing width so that a larger bearing area is provided to support the facing element.
To enhance the ability of the wall to support the vegetative material, a layer of topsoil may be placed along the horizontally extending area at the base of each row of wall facing elements. This topsoil may, in fact, be banked toward the face surface of the wall facing panels, as desired.
In some instances, to avoid percolation of surface water through vertically extending joints between adjacent wall facing panels, each wall facing panel may be provided on its back surface with a pair of ribs, each rib being positioned adjacent to a vertical edge. With panels in sidewise adjacent relationship, a channel member that may be generally U-shaped is positioned over the projecting ribs of adjacent panels to cover the vertical joint therebetween. In this manner, ground surface water which percolates down the rear surface of the wall facing elements is channeled into the particulate backfill material by the large channels defined between the ribs of each panel.